The essential constituents in commercial epidermal cleaning compositions are an antiseptic agent and a surfactant; however the final composition should exhibit high foaming, good water solubility, adequate detergency and acceptable organoleptic characteristics. Formulation of epidermal cleaning compositions containing conventional antiseptic agents has been problematical due to incompatibilities resulting from (1) destruction of the activity of said antiseptic agents, (2) phase incompatibility of said antiseptic agents, (3) long-term stability of said antiseptic agents in highly detergent compositions, and (4) achieving acceptable organoleptic properties. This application discloses the use of a composition containing peroxidase, peroxide and iodide in a prescribed formulation suitable for use as an antiseptic agent to form a disinfecting epidermal cleaner which does not suffer from the above incompatibilities.
For the peroxidase based composition of the subject invention to provide antiseptic activity in an epidermal cleaner the following must be achieved: (1) the maintenance of enzymatic activity, (2) the maintenance of substrate (peroxide and iodide) concentrations within a defined range, (3) the absence of molecules or reaction by-products which meaningfully compete with iodide or peroxide for the active site of the enzyme, (4) the diffusion of the nascent bactericidal iodide radical (or by-product) from the enzyme's active site to targeted organisms, and (5) the absence of vitiating interactions between the bactericidal iodide free radicals (or by-products) and other components in the environment. The possibility of creating an effectual disinfecting epidermal cleaner whose biocidal ingredients are comprised of peroxidase, peroxide and iodide, can only be accomplished if the five requirements listed above are substantially met.
It is known from Kessler (U.S. Pat. Nos. 4,476,108, 4,588,586 and 4,473,550), Orndoff (U.S. Pat. No. 4,370,199) and Montgomery (U.S. Pat. No. 4,576,817) that a composition of peroxidase, peroxide and a source of donor molecules will form a bactericide in an aqueous non-viscous solution. The source of donor molecules must be capable of dissolving in water in order for the system to function as a disinfectant. For purposes of the present invention non-viscous means a viscosity of less than 1.2 centipoises. The disinfecting applications described in the above identified patents take place either in a totally aqueous environment or upon a meaningful dilution or dissolution (greater than 10 fold) of a formulation to form a substantially aqueous environment. None of the previous applications involve disinfecting environments which are viscous and/or contain high concentrations of surface active agents required for a useful disinfecting epidermal cleaner.
The present invention may be used to disinfect any epidermal surface on either a human or animal. In fact the present invention is particularly suited to the treatment of bovine mastitis.
The viscosity of commercial liquid soap cleaners am often at least about 5 centipoises and are typically above 20 centipoises and sometimes greater than 100 centipoises. The viscosity inherent to liquid epidermal cleaning compositions will reduce the diffusion of molecules relative to that in a substantially aqueous environment. The short-lived lifetime of the free radical (or by-products) generated by the removal of an electron from a donor molecules imposes a constraint upon a system which requires an enzymatic reaction to occur between peroxidase, peroxide and donor molecules. The free radicals (or by-products) generated at active site of peroxidase must have enough time to diffuse to their ultimate site of action in order for the system to be effective. The diffusion coefficient, which is proportional to the rate of motion of a molecule in a matrix, is inversely proportional to the viscosity of a matrix. Accordingly, the viscosity inherent in the high concentrations of surface active agents, including; unsaturated fatty-acids, could be expected to decrease or eliminate the disinfecting ability of this system.
In traditional cold chemical disinfectants are used by forming a homogeneous solution/suspension of the disinfecting chemical provides a known concentration of active species throughout the environment. That is, with traditional cold disinfectants there exists a known evenly distributed concentration of stable disinfecting agents at the outset of a disinfection regime. These disinfecting agents are free to diffuse through solution and contact pathogenic organisms of interest. Through trial and error, the concentration of the chemical disinfecting agents is chosen such that there are enough molecules of the disinfectant to contact pathogen organisms in the desired time frame to effect the desired biocidal activity.
Unlike traditional cold chemical disinfectants, the peroxidase system of Kessler relies upon an enzymatic reaction to generate disinfecting species. The full disinfecting cycle consists of the following reactions: (1) hydrogen peroxide must diffuse to the active site of the enzyme; (2) a molecule of water must diffuse from the active site of the enzyme; (3) an iodide molecule must diffuse to the active site of the enzyme; (4) the enzymatic by-product of iodide oxidation must diffuse from the active site of the enzyme; (5) another iodide molecule must diffuse to the active site of the enzyme; (6) a water molecule must diffuse from the active site of the enzyme; (7) an active intermediate must diffuse from the active site of the enzyme; and (8) the active intermediate must survive long enough to collide with a pathogen of interest. The Stokes-Einstein relationship defines the overall diffusion of a molecule as a function of viscosity. This equation indicates that diffusion is inversely related to viscosity. Thus for every 10% increase in viscosity the rate of diffusion of a species in solution is slowed by a factor of 9.1%.
Moreover, unlike traditional chemical disinfectants, the peroxidase system of Kessler relies upon a series of chemical reactions with each of these reactions expected to be slowed by an increase in viscosity. That is, a reduction in the rate of diffusion will effect each of the individual reaction steps in Kessler which comprise a full disinfecting cycle. In particular, a significant increase in viscosity would be reasonably anticipated to have a significantly effect on step 7 (the active intermediate must diffuse from the enzyme) and step 8 (the active intermediate must collide with a pathogen) which are critical for disinfection. The reason that these steps would be anticipated to be especially sensitive to a reduction in their diffusion associated rate constant is that the active disinfecting agent is a by-product of the enzymatic reaction generated within the active site of the enzyme a significant distance from pathogens that are the desired site of activity. Thus it is reasonably inferred that the biocidal species might not survive long enough to collide with pathogens.
In Karo (U.S. Pat. No. 4,485,029) a composition is taught for cleaning, disinfecting and preserving contact lens comprised of glyceryl monolaurate in combination with antimicrobials, organic surfactants, alkali metals, adjuvants and buffer. This type of product includes surface active agents but not in a viscous environment since this would obstruct cleaning and potentiate the possibility for eye irritation. The viscosity of all of the formulations taught in Karo lie within the viscosity range between 1.010 to 1.060 centipoise.
It has been discovered in accordance with the present invention that a composition of peroxidase, peroxide and a source of a donor molecule can form an antiseptic agent for use in an aqueous epidermal cleaner under conditions of high viscosity by using iodide as the donor molecule and by controlling the pH of the aqueous composition between a pH of 3.0 to 6.5. Viscosity is a critical element of this invention since it is a required property of many products like certain soaps and bovine teat disinfectants. For purposes of the present invention, the relative viscosity of a disinfecting composition can be measured using an Ostwald viscometer by measuring the amount of time it takes for the liquid level to fall through a defined length of a capillary tube. The relative viscosity of a formulation is then calculated by comparing the time required for the formulation to fall divided by the time required for distilled water to fall the equivalent distance. The epidermal cleaner may have a high concentration of surface active agents with a viscosity above 1.2 centipoises to assure satisfactory cleaning simultaneously with disinfection. The epidermal cleaner of the present invention broadly comprises a surface active agent, an antiseptic agent including peroxidase, a source of peroxide, and an iodide compound in combination with a buffering system to cause a pH of between 3.0 and 6.5 when the cleaner is diluted with water over a dilution range of about 10 to 1 water to cleaner. The subject invention contemplates the use of any buffering system in conjunction with or without an inert carder to cause equilibration of the composition in water with a pH in the final admixture of between 3.0 and 6.5 over a wide dilution range.